A child with presumptive monosomy 21 (45,XY,–21) in a family in which some members are Gq–

Abstract

Presumptive monosomy for chromosome 21 was found in a male child with multiple malformations and severe psychomotor retardation. Chromosome analyses of cells from blood and skin samples were performed at intervals during the first few years of his life. In preparations stained with nonbanding as well as quinacrine, Giemsa, and reverse acridine orange banding techniques, only one No. 21 chromosome could be detected with no apparent abnormalities of the other chromosomes. The proband’s phenotypically normal father, paternal grandfather, brother, and paternal aunt have a deletion for a short segment of the long arm of a G-group chromosome. Genetic-marker studies allow the exclusion of a number of blood groups as being associated with No. 21. There is inconclusive evidence suggesting that expression of the Duffy blood group, which has been mapped to chromosome 1, may be influenced by genetic information on chromosome 21. This family is of potential value for further gene-mapping studies.

Full Monosomy 21, Prenatally Diagnosed by Fluorescentin Situ Hybridization

“…Cleft lip and/or palate have been described in many cases of supposed full (Dziuba et al, 1976;Fryns et al, 1977;Houston and Chudley, 1981) and partial monosomy 21 (Davis et al, 1976;Jamehdor et al, 1978;Philip et al, 1984;Bartsch et al, 1994). However, most of the eye abnormalities that were found have never been reported before in monosomy 21.…”

Down syndrome: Gene dosage at the transcriptional level in skin fibroblasts

“…Gene dosage (determined by cellular enzyme activity measurements) has been documented for a number of enzymes in human beings (46), including superoxide dismutase-1, which has been mapped to chromosome 21 (20)(21)(22)(23). Gene dosage effect for superoxide dismutase-1 has been shown in a variety of cell types, including skin fibroblasts from subjects with Down syndrome (trisomy 21), normal subjects (disomy 21), and the same monosomy 21 fibroblast line (19) used in this study (20). Thus, the increased chromosome 21-specific transcriptional product detected in this study appears, at least for superoxide dismutase-1, to be actively translated and to result in increased chromosome 21-coded protein product.…”

“…The monosomy 21 skin fibroblast line is derived from a 5-year-old boy and was obtained from the Human Genetic Cell Repository (Camden, NJ) (cell line GM-137). The diagnosis of monosomy 21 for this skin fibroblast line has been confirmed by a variety of banding techniques in several laboratories (19). In addition, this line was used -in biochemical studies (20) that demonstrated 60% of the normal level of superoxide dismutase, an enzyme that has been mapped to chromosome 21 (21)(22)(23).…”

Monosomy 21: A possible stepwise evolution of the karyotype

“…Although complete monosomy 21 has been reported in only a few instances [Gripenberg et al, 1972;Halloran et al, 1974;Davis et al, 1976;Fryns et al, 19771 , these patients share many clinical characteristics so as to suggest a recognizable syndrome consisting of intrauterine growth retardation, failure to thrive, craniofacial anomalies, arthrogryposislike features, and psychomotor retardation. Our patient presents with a phenotype closely resembling that of complete monosomy 21 (Table HI).…”